1. Field of the Invention
This invention relates generally to medical instruments for retrieving and withdrawing clots from the vasculature, and more particularly concerns a shape memory clot retrieval device having an elongated catheter member with at least one clot retrieval member connected to the elongated catheter member that is movable between an initial compressed configuration in which the clot retrieval device is inserted into the vasculature and an expanded configuration extending outwardly from the elongated catheter member to trap and hold clots within the vessel.
2. Description of Related Art
Recently developed interventional procedures have been used to treat defects in the vasculature which are not easily reached by surgical procedures. More particularly, such interventional procedures have been developed to treat defects that are located in small and remote vessels such as those within the brain. During such interventional procedures, vasoocclusive devices are typically placed within the vasculature of the human body by use of a catheter, either to block the flow of blood through a vessel making up that portion of the vasculature through the formation of an embolus, or to form such an embolus within an aneurysm stemming from the vessel. When an embolus generating vasoocclusive device is used to treat an aneurysm, the success of the treatment generally depends upon whether the embolus generating vasoocclusive device can migrate out of the aneurysm through the neck of the aneurysm. Migration of the embolus generated out of the aneurysm into the parent vessel poses a danger to the patient, so that it would be desirable to provide a device for retrieving and withdrawing such an embolus, whether the embolus has been created by an embolus generating vasoocclusive device or otherwise.
One conventional technique for retrieving deleterious materials such as an embolus from body lumens involves the use of a retrieval catheter having a slack net at its distal end that is operated by a pull wire, that may be collapsed to facilitate introduction of the catheter into a body lumen, and that may be opened when necessary to permit capture and retrieval of the deleterious materials. The slack net structure is secured to a flexible loop member which is secured to the pull wire, and the flexible loop member is formed from resilient materials possessing a memory so that when pull wire is retracted, the loop member will regain a preset circular configuration. However, such a structure is relatively bulky and cumbersome, making the technique difficult to employ in more distal areas of the vasculature with narrow lumens, such as in the brain.
A catheter apparatus is also known that employs a shape memory alloy structure as an actuator for a thin shutter door to open and close a radially disposed opening in the catheter for collecting plaque. While this apparatus is suitable for collecting plaque on the inside of a blood vessel, it is not generally effective for retrieving and withdrawing an embolus that may be loose or free floating within the vasculature. Another known technique uses an adjustable closed wire loop or snare that is manipulated over an object to be retrieved, and in one such apparatus, the surgical snare is made from a shape memory material that can be trained to remember a specific configuration. However, these types of surgical snares can require great care and dexterity for their operation in acquiring an embolus, and an embolus can easily escape, so that it would be desirable to provide a system for retrieving and withdrawing an embolus within the vasculature of a patient that can be deployed in narrow, distal vessels for trapping and holding distal loose or free floating clots. The present invention meets these needs.